Tire tread is also designed to look good. Some of the reasons that the tread on your tires looks the way it does are simply marketing. But that doesn’t mean that the grip is compromised. The evolution of tires is incredibly complicated and involves many factors. So two tread patterns or even two compounds with significant differences can produce about the same grip.
Goodyear’s engineers stretched the development process well beyond the usual boundaries while working on the Ventura and the team conceived new tools such as Fluid Dynamics modeling. It led to several tire technology breakthroughs under the banner of V tread technology. This technology uses a silica-based tread compound, assures a good stiffness distribution in the tread without sacrificing any aquaplaning resistance.
Treads are specially shaped dux in the tread pattern, increasing water dispersion like the aqua tread, providing unprecedented resistance to aquaplaning. Noise levels are also reduced from the outgoing and C2 Tire.
Many other tires these days have been designed with safety in mind. We’re going to figure out the secrets behind tires’ grip. Why are there many tread variations in a simple design, and why do some tires cost more than your average new car? Let’s figure it out.
Why do tires have treads?
About 99% of the time, the tread eliminates as much water as possible between the tire and the road surface. Any water in there can work as a lubricant and reduce the amount of grip. If there’s enough water between the tire and the road, aquaplaning will remove the contact entirely. Aquaplaning is a situation where the tire no longer touches the ground, and at that point, you have no control over the vehicle.
- The tread’s job is to delay the onset of aquaplaning as much as possible.
If you look at the pattern on the tread, you can see two surfaces.
- The one on top touches the road, and the one at the bottom doesn’t even touch the road until the tire wears out.
Let’s call these the positive surface and the negative surface for convenience.
- The positive surface’s job is effectively what the tire is supposed to do. It transfers your control inputs to the road so that the vehicle responds as you want it to.
When you use the brakes, the reverse happens, where the positive surface in contact with the ground will deform. That will allow your braking input to be turned into retardation. It’s the same when you turn the vehicle’s handlebar as well.
- The negative surface gives a channel to the water so that the pressure of the positive surface diverts the water into the negative channels. Also, these channels allow the water to exit the scene rather than get between the positive surface and the road touching.
That’s what a tread does. But, tread designs can be optimized to make less noise because treaded tires make a lot of road noise. Tread can also have sipes which are incredibly narrow channels.
You’ll usually see them on low-performance vehicles because they have the time to use the sipe to evacuate water, whereas a fast-moving vehicle will not give the sipes enough time to do anything. Therefore high, performance tires will have some amount of tread.
How does tire tread work?
Let’s look at the chemicals inside the tread itself and why those are so important. Most attire is composed of 20% natural rubber, combined with synthetic rubber and other chemicals to make a material that grips. The exact mixture of those chemicals is a tire compound and creation that requires a unique process: Vulcanization.
Vulcanization is essential because natural rubber is problematic, like Nolan, for tires. When it’s too cold, it gets tough and can crack. But when it’s too warm, it gets soft and can be easily punctured. Vulcanization is the process of heating rubber with other chemicals so that they bond together. These chemicals include synthetic rubbers and pliant at different temperatures compared to natural rubber.
- Carbon increases wear resistance, transmits heat for even tire temperatures, and gives tires their black color, helping them resist UV damage.
- Silica decreases rolling resistance to reduce noise and improve fuel economy.
- The final mixture of the compound has texture and thermal properties different from natural rubber.
These will determine how well the tire grips. That brings us to one of the most important factors that make a tired stick to the road: tread pattern. You can easily see that a snow tire, an all-season tire, and a performance tire have different tread patterns. Those differences are crucial to producing grip, particularly when conditions aren’t ideal. Ideal conditions are what you find on a racetrack. You got dry pavement, warm temperatures, and clean asphalt.
- Race tires don’t have a pattern in their tread because they don’t need it. They only need to deal with one consistent track surface. But if you plan to take your car on or off-road, your tread pattern helps maintain grip as conditions change.
A tire’s tread pattern can be broken down into a few parts: The large, raised pieces of rubber that make contact with the road are called tread blocks. Or, in the case of off-road tires, lugs. Collectively, these are called ribs. As they have some ability to move around, they allow the tire to flex and adapt to the road’s surface.
Between the blocks and the ribs are grooves or voids. The even smaller lines in the tread blocks are called sipes. You’ll also find wear bars inside the grooves in most tread patterns. These are there to tell you when it’s time for new tires. When the tread wears down to those bars, the pattern is only about 2/32 of an inch deep. The blocks are shorter and less flexible, and the grooves are shallow.
- The tread pattern’s ability to produce grip depends on those grooves because that’s how the tread pattern prevents hydroplaning on the road.
Water can drastically change the coefficient of friction between two objects. In the case of rubber and concrete, it takes less than a third of the force to make rubber lose grip on wet concrete than dry concrete.
Water creates a barrier between those two objects, preventing them from making full contact. It fills in the roughness, which would add to grip, and hydroplaning happens when there’s so little contact between the tire and a wet road that it slides. The lateral grooves and sipes on a tire give the blocks a leading edge on their approach to the wet road surface.
- The tread blocks on a tire rotate quickly to move enough water and prevent hydroplaning unless the water has somewhere to go. These provide channels for water to get pushed out. Out of the way of the tread blocks so they can make contact with the road.
- The same principle helps move small particles of loose sand, gravel, or snow away from the tread block so the tire can grip the road surface beneath.
- A tread pattern with a large contact patch for dry asphalt will only have grooves capable of moving small amounts of water and can be overwhelmed in a downpour.
A tire that can move large amounts of water has to have large grooves and, therefore, a reduced dry contact patch. But tires have had 170 years to evolve. There are ways to reduce these compromises with cleverly engineered patterns. Most tread patterns on passenger tires are fully symmetric. That means the tread is the same on the left and right sides, coming and going.
Why tire tread is so important?
A tire’s job is to make a grip, but this idea isn’t frigging new. Thousands of years ago, leather and iron were added to the surface of wooden wheels to aid in traction. But the basic design for inflatable rubber tires is only about 170 years old. It might look like a tire is a single piece of molded rubber from the outside. Modern tires contain only 20% natural rubber and can include up to 200 other chemicals in the compound.
It might also seem the key to grip is all in the tread since that’s the part that touches the road. Three factors explain how a modern tire does its job.
- The construction supports the tread, the compound it’s made from, and its tread pattern.
Tires have as many as 25 individual components that must be manufactured separately and bonded together during construction. Every modern tire shares some essential parts.
- Tread is designed to contact the road, and a sidewall has dozens of letters, numbers, and symbols. Each of which tells you something about that tire.
So to understand grip, we’ve got to look from the inside out. The structure and basic shape are provided by what’s called the carcass. The carcass is made of rubber-coated fabric, usually polyester. Fine textile strands are woven to give the tire a strong but flexible base. These are sometimes called cords, and a corded tire has been worn or damaged to the point that the fibers are visible from the outside.
- The carcass determines how much weight and inflation pressure attire can withstand.
- Visible cords mean the internal structure can no longer do that job safely.
Driving on corded tires is incredibly dangerous. In addition to fabric, tires also contain metal. The bead includes a wire at the base of the sidewall.
- The air pressure inside the tire presses the bead into a groove on the wheel in that rigid metal wire, ensuring the tire doesn’t pop out.
There’s also the belt. That’s usually made from a combination of nylon and strips of steel, often in a criss-cross or lattice pattern to give it strength. Expensive tires may even include Kevlar for even more strength and resistance to puncture.
- The fibers in the carcass are laid perpendicular or radially to the direction of the tires’ travel. They act as springs to absorb bumps from the road and provide a comfortable ride. But radial fiber wheels don’t provide much support to the tread.
The steel belt works together with the carcass to ensure that the tire is rigid enough to stay in contact with the road when going over bumps. In other words, it maintains grip.
Nearly every tire since the 1960s uses this combination of radial fibers and steel belts. But back then, it was a revolutionary design. Modern tires are sometimes called steel-belted radials to distinguish them from older designs that lack those features.
Tread’s job is to remove water between the tire and the road so that you can continue to accelerate, decelerate, and turn on a motorcycle/car.
Pay attention to tread depth because as the depth gets less, the amount of water we can remove becomes less. That means the amount of grip you will have available starts to become less and less to the point where it’ll become zero. You change your tire when 1mm of tread depth is left because you never want the situation to hit zero.
Learn more similar topics:
Michael Hogan, Analysis of highway noise, Journal of Water, Air, & Soil Pollution.
Tires with Smooth Tread by Jobst Brandt. (Tire Deals)